EP0324720B1

EP0324720B1 - Saccharide inhibition of dental plaque

Info

Publication number: EP0324720B1
Application number: EP89810013A
Authority: EP
Inventors: Donald Michael Lynch; Benjamin Appelbaum
Original assignee: Warner Lambert Co LLC
Current assignee: Warner Lambert Co LLC
Priority date: 1988-01-14
Filing date: 1989-01-09
Publication date: 1991-12-18
Anticipated expiration: 2009-01-09
Also published as: AU2664088A; NZ227612A; EP0324720A1; JPH01213222A; GR3003395T3; DE68900547D1; PT89455A; ZA889112B; PH25171A; US4855128A

Description

This invention is concerned with a method of inhibiting the formation of dental plaque which employs certain saccharides and oral compositions containing such saccharides.
Dental plaque is a dense, heterogeneous, non-calcified bacterial mass which firmly adheres to the tooth surface to the degree that it resists wash off by salivary flow. The bacteria contained in plaque possess varying degrees of pathogenic activity and are responsible in part for dental caries, gingivitis, mouth odour and periodontal disease. Streptococcus mutans is one of the bacteria found in dental plaque and it has been found to possess a high cariogenic potential in a variety of laboratory animals. Actinomyces viscosus, another dental plaque bacteria, has been associated with gingivitis and root surface caries. Obviously the removal or inhibition of plaque formation would significantly reduce the occurences of these diseases.
Plaque is generally removed by employing mechanical cleaning, using an abrasive dentifrice, by flossing or by rinsing with an antibacterial (anti-plaque) mouthrinse. However, plaque deposited between teeth is difficult to remove by mechanical cleaning and flossing does not remove plaque located at the gingival margin. Anti-plaque mouthrinses serve as an adjunct to mechanical plaque removal. To date, an anti-plaque mouthrinse that can take the place of mechanical plaque removal has not been discovered.
Plaque formation on a clean tooth, it is generally believed, starts with the formation of a pellicle or cuticle composed of salivary constituents. The pellicle is an amorphous, membranous layer which covers the enamel surface and is considered to consist of salivary glycoproteins, polypeptides and other salivary constituents which have become selectively adsorbed on the tooth surface. The pellicle is usually free of bacteria. The pellicle is formed within minutes after the tooth is cleaned and the adsorbed materials eventually become transformed into a highly insoluble coating. Thereafter an initial adherence of specific bacteria occurs on the acquired pellicle. These bacteria produce extracellular polysaccharides (called glucans) from sucrose catalyzed by the enzyme glucosyl transferase which aid entrapment and adherence of other bacteria.
The cariogenic potential of S. mutans for example is associated with its ability to form dental plaque and this ability is dependent upon the synthesis of extracellular polysaccharides from sucrose. In addition to initial adherence, the coaggregation of various species of bacteria occurs in which specific bacteria attach to each other by synthesizing polymers which bind similar and dissimilar cells together although there are some species that will not coaggregate.
In an effort to rid teeth of plaque the prior art has described agents incorporated into oral preparations such as dentifrices which inhibit the formation of plaque rather than its removal as described above.
In U.S. Patent No. 4,117,107 for example, a method for retarding pellicle and plaque formation is described which includes contacting sites of plaque formation and growth with a dental preparation containing certain fatty acid amido betaines.
Similarly, U.S. Patent No. 4,130,637 provides betaine compounds derived from higher alkyl dimethyl carboxylic acid quarternary ammonium compounds effective in controlling dental plaque without producing an esthetically unacceptable discoloration of the teeth.
U.S. Patent No. 4,360,515 provides compounds for the prevention of attachment of dental plaque to the teeth comprising certain sulphonated alkoxynaphthalenes and the pharmaceutically acceptable salts thereof.
U.S. Patent No. 4,619,825 describes a plaque-inhibiting composition comprising an aqueous dispersion of emulsan which can be incorporated in dental preparation toothpastes or mouthwashes.
The present invention, on the other hand, provides an effective plaque inhibiting composition containing certain saccharides which act to prevent the coaggregation of bacteria in the formation of plaque and therefor substantially inhibit its complex formation. The saccharides are non-toxic, suitable for oral application in most oral compositions and are effective at low concentrations.
In brief, the invention comprises an oral composition containing certain agents which inhibit the coaggregation of bacteria and thereby inhibit the complete formation of plaque. The various aspects of the invention are as detailed in the claims. The polysaccharide anti-plaque agents can be used in aqueous-based oral compositions at concentrations of between 0.0025% and 2.000% on a weight/volume basis to be effective in inhibiting coaggregation.
The plaque inhibitory agents of the present invention include certain naturally-occuring saccharides which inhibit the interaction of oral microorganisms or bacteria to substantially prevent coaggregation thereby reducing or eliminating the build up of plaque. These saccharides comprise polysaccharides such as xanthan gum, gum tragacanth, pectin, guar gum, gum karaya, chondroitin sulphate, polygalacturonic acid, sodium alginate and carrageenans of the kappa/lambda configuration. Many of the polysaccharides useful herein such as xanthan gum and gum tragacanth have previously found application as inert ingredients in formulations containing pharmaceutically active agents as for example binders, stabilizers or thickeners. However, these saccharides are not known to possess any biological or pharmaceutical activity in and of themselves. Other agents described in this invention such as chondroitin sulphate are used as antihyperlipoproteinemic or wound healing preparations. None of the saccharides have been described heretofore as anti-plaque agents.
The agents can be incorporated in any aqueous-based oral composition such as a mouthwash, toothpaste and the like and will effectively inhibit plaque formation at concentrations which are far less than their normal use levels in other compositions. Generally they can be used at concentrations of between 0.0025% and 2.000% and preferably between 0.05% and 1.0% (weight/volume basis) to inhibit coaggregation. For example, guar gum and xanthan gum which are normally used in foods at levels up to an often greater than 3% to 4% on a weight/volume basis show anti-plaque activity in aqueous media at levels between 0.15% and 0.07% on the same basis.
An assay was developed to determine the inhibition of coaggregation of Streptococcus sanguis and Actinomyces viscosus, two organisms commonly found in plaque. Polygalacturonic acid was found to inhibit at low concentrations (approximately 2 mM). Xanthan gum, guar gum and gum tragacanth are also extremely effective, effecting 50% inhibition of coaggregation at concentrations of 0.05%, 0.15% and 0.35%, respectively. Gum Tragacanth contains mostly galacturonic acid.
Pectin, chondroitin sulphate and sodium alginate demonstrate substantial inhibition according to the assay. Carrageenans of the kappa and lambda configuration show moderately effective inhibition but carrageenans of the iota configuration exhibit poor inhibitory characteristics.
The anti-plaque agents of the invention can be readily incorporated into aqueous or aqueous/alcohol-based oral compositions such as a mouthwash, spray, rinse, toothpaste, dental cream, gel or toothpowder.
The agents should be present in amounts of from 0.0025% to 4% by weight of the total weight of the composition. Preferably the complex is present in amounts from 0.01% to 2% by weight of the total weight and most preferably from 0.05% to 1.0%.
In one form of the invention, the oral composition may be a liquid such as a mouthwash, spray or rinse. In such a composition the vehicle is typically a water/alcohol mixture. Generally the ratio of total water to alcohol is in the range of from 1: 1 to 20: 1, preferably 3: 1 to 20: 1 and most preferably 3: 1 to 10: 1 by weight. The total amount of water/alcohol mixture in a mouthwash preparation is typically in the range from 45% to 82.5% by weight of the composition. The pH value of such mouthwash preparation is generally from 4 to 9 and preferably from 5 to 8.5. A pH below 4 is irritating to the oral cavity and a pH greater than 9 results in an unpleasant mouth feel.
Fluorine providing compounds may be present in the oral preparations of this invention. These compounds may be slightly water-soluble or may be fully watersoluble and are characterized by their ability to release fluoride ions or fluoride containing ions in water. Typical fluorine providing compounds are inorganic fluoride salts such as soluble alkali metal, alkaline earth metal, and heavy metal salts, for example, sodium fluoride, potassium fluoride, ammonium fluoride, cuprous fluoride, zinc fluoride, stannic fluoride, stannous fluoride, barium fluoride, sodium fluorosilicate, ammonium fluorosilicate, sodium fluorozirconate, sodium monofluorophosphate, aluminum mono- and difluorophosphate and fluorinated sodium calcium pyrophosphate.
Alkali metal, tin fluoride and monofluorophosphates such as sodium and stannous fluoride, sodium monofluorophosphate and mixtures thereof are preferred.
In an oral liquid composition such as a mouthwash, the fluorine providing compound is generally present in an amount sufficient to release up to approximately 0.15%, preferably 0.001% to 0.1% and most preferably from 0.001% to 0.05% fluoride by weight of the preparation.
The oral composition may also contain additional flavourants and colourants.
In the instance where auxiliary sweeteners are utilized, the present invention contemplates the inclusion of those sweeteners well known in the art, including both natural and artificial sweeteners. Thus, additional sweeteners may be chosen in minor amounts from the following non-limiting list.

A. Water-soluble sweetening agents such as monosaccharides, disaccharides and polysaccharides such as xylose, ribose, glucose, mannose, galactose, fructose, dextrose, sucrose, maltose, partially hydrolyzed starch or corn syrup solids and sugar alcohols such as sorbitol xylitol, mannitol and mixtures thereof.
B. Water-soluble artificial sweeteners such as the soluble cyclamate salts and the like.
C. Dipeptide based sweeteners such as L-phenylalanine methyl ester and materials described in U.S. Patent No. 3,492,131 and the like.

In general, the amount of sweetener will vary with the desired amount of sweeteners selected for a particular oral preparation. This amount will normally be 0.01% to 40% by weight. The water-soluble sweeteners described in category A above, are preferably used in amounts of 5% to 40% by weight, and most preferably from 10% to 20% by weight of the final composition. In contrast, the artificial sweeteners described in categories B and C are used in amounts of 0.005% to 5.0% and most preferably 0.05% to 2.5% by weight of the final composition. These amounts are ordinarily necessary to achieve a desired level of sweetness independent from the flavor level achieved from flavourants.
Suitable flavourings include both natural and artificial flavours, and mints such as peppermint and spearmint. Citrus flavours such as orange and lemon, various fruit flavours, both individual and mixed, and the like are contemplated. The flavourings are generally utilized in amounts that will vary depending upon the individual flavour, and may, for example, range in amounts of 0.05% to 6% by weight of the final composition.
The colourants useful in the present invention include the pigments which may be incorporated in amounts of up to approximately 2% by weight of the composition. Also, the colourants may include other dyes suitable for food, drug and cosmetic applications, known as FD & C and D & C dyes. The materials acceptable for the foregoing spectrum of use are preferably water-soluble. Illustrative examples include the yellow dye, known as D & C Yellow #10, and the dye known as FD & C Green #3 which comprises a triphenylmethane dye. A full recitation of all FD & C and D & C colourants useful in the present invention and their corresponding chemical structures may be found in the Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Edition, in Volume 6, at pages 561-595.
The oral compositions may also be substantially solid or pasty in character such as a dental cream, toothpaste or a toothpowder. Solid or pasty oral preparations contain polishing materials. Typical polishing materials are abrasive particulate materials having particle sizes of up to approximately 20 micrometres. Nonlimiting illustrative examples include: water-insoluble sodium metaphosphate, potassium metaphosphate, tricalcium phosphate, dihydrated calcium phosphate, calcium pyrophosphate, magnesium orthophosphate, trimagnesium phosphate, calcium carbonate, alumina, aluminium silicate, zirconium silicates, silica, bentonite, and mixtures thereof. Polishing materials are generally present in an amount from 20% to 82% by weight of the oral preparation. Preferably, they are present in amounts from 20% to 75% in toothpaste, and from 70% to 82% in toothpowder. For toothpaste and dental creams the water content is 25% to 50% by weight.
In clear gels, a polishing agent of colloidal silica and alkali metal aluminosilicate complexes are preferred since they have refractive indicies close to the refractive indicies of gelling agent liquid systems commonly used in dentifrices.
In general, the anti-plaque oral compositions of the present invention are prepared as follows. The sweetener is dissolved in water to form a solution. The anti-plaque agent is added to the solution and mixed until dissolved. Then sufficient water alcohol or mixtures thereof are added with mixing until the final solution volume is reached. When colourants, additional sweeteners and similar additives are included in the composition, they are added at the same time the sweetener is added. The anti-plaque agent may also be added as the final ingredient.
In order to more fully describe the present invention, the following Examples are submitted.

Example 1

This Example describes an assay for determining the inhibition of coaggregation by various agents according to the invention and the results obtained thereby.

A. Preparation of Growth Medium:

Streptococcus sanguis strain 34 (originally derived from human dental plaque), and Actinomyces viscosus T14V were grown in a medium containing the dialyzable portion of Trypticase and Yeast Extract, supplemented with salts and a carbon source, as follows: A concentrated stock solution (20X, to make 10 litres of growth medium) containing Trypticase Peptone (BBL, 170 grams) and Yeast Extract (40 grams) as prepared in a litre of distilled water. This solution was subsequently ultrafiltered in an Amicon™ model DC-2 hollow fibre ultrafiltration cell, using an H1P10-20 hollow fibre cartridge (molecular weight cut off of 10,000 daltons), and the filtrate (that material of < 10,000 daltons molecular weight) saved. The material was concentrated to a final volume of approximately 100 ml, and then reconstituted to one litre, after which the procedure was repeated for a total of three cycles, saving the filtrates at each step. The filtrates were collected into a vessel chilled on ice, combined, and the total volume measured. This stock solution was distributed in aliquots sufficient to make one litre of medium, and stored at -20°C until used.
To prepare the growth medium, the appropriate volume of the 10X stock Trypticase-Yeast Extract stock solution was thawed, and to it added (in grams per lire): NaCl, 5, and K₂HPO₄, 2.5, and the volume adjusted to 1 litre with distilled water. The medium was sterilized by autoclaving. Where indicated, glucose was added as a carbon source to give a final concentration of 0.2%. Initially, this was done by aseptically adding filter-sterilized glucose solutions to the autoclaved medium. For later experiments, glucose was added to the growth medium prior to sterilization.

B. Growth Conditions:

Streptococci were grown in medium containing 0.2% glucose. Starter cultures were prepared by inoculation from a frozen stock culture, and incubated overnight at 37°C under aerobic (not anaerobic) conditions. This starter culture was used as a 0.5-1.0% inoculum to inoculate larger quantities of medium (100 m1-1 litre), which were subsequently incubated for 16 hours at 37°C. Growth conditions were similar for the actinomycete, except that they were grown under an anaerobic environment (10% hydrogen-5% carbon dioxide, and 85% nitrogen). The starter culture was incubated for 24-48 hours, but the larger cultures required 48 hours incubation.

C. Preparation of Cells for Coaggregation Assays:

After growth, the cells were collected by centrifugation (10,000 x g, 15 minutes, 4°C) and washed three times in PBS (phosphate-buffered saline, 0.025 M, pH 8.0 containing 1.46 g NaCl per litre). The cells were then suspended in PBS such that when the stock cell suspension was diluted 1: 10, it would produce an Absorbance at 660 nm of between 0.22-0.24, equivalent to an initial Absorbance of 2.2-2.4. The cells were stored on ice for use during the day, but warmed to ambient temperature before initiation of coaggregation. Residual cells were stored for further use by resuspension in a solution of 50% glycerol in water, and stored at 4°C. On the day of use, the cells were then collected by centrifugation, washed twice with PBS, and the trubidity adjusted as described above. It has been found that cells could be stored for at least 2 months under these conditions with no significant loss of coaggreating activity.

D. Coaggregation Assay:

Assays were performed in a final volume of 1.0 ml in 190 × 75 mm disposable culture tubes, in duplicate. Controls consisted of 0.8 ml of either cell suspension, and 0.2 ml PBS. The coaggregating mixtures contained 0.4 ml of each cell suspension, and PBS to make 1.0 ml. Inbibitors were added from stock solutions to give the desired final concentrations, and, where necessary, the salt concentrations adjusted using a double-strength (2X) PBS solution. The mixtures were mixed on a Vortex™ mixer for 10 seconds at a speed setting of 6, incubated at ambient temperature for 10 minutes, mixed again, and allowed to stand for 2 hours. After the 2 hours, the mixtures were again mixed, and evaluated visually and quantitatively.

1. The scale for visual evaluation of coaggregation is:
Score: Criteria:

Zero

No visible aggregates in the cell suspension.

Plus 1

Small uniform aggregates in suspension.

Plus 2

Definite coaggregates easily seen but suspension remained turbid without immediate settling of coaggregates.

Plus 3

Large coaggregates which settled rapidly, leaving some turbidity in the supernatant fluids.

Plus 4

Clear supernatant fluid and large coaggregates which settled immediately.
2. To quantitate coaggregation, tubes containing the reaction mixtures were centrifuged in an IEC™ Clinical Centrifuge (using an IEC™ #215 rotor with IEC™ #369 multiple tube carriers). After a 1 minute centrifugation (ambient temperature, speed setting of 2), the supernatant fluids were withdrawn, and their Absorbance at 660 nm (A₆₆₀) determined using a spectrophotometer. These centrifugation conditions enabled the separation of the coaggregates from the free cells remaining in the mixture. Coaggregation was then quantitated using the following formula:

The percent coaggregation in the presence of an inhibitor is normalized to that of the control, and percent inhibition is 100% minus the percent coaggregation in the presence of inhibitor.
The data is plotted semi-logarithmically, and the concentration of a given agent that is able to effect 50% inhibition of coaggregation is then determined from the graph. The data reported represents the average from two independent experiments, each run in duplicate.

Examples 2 & 3

The agents of the present invention were tested for coaggregation inhibition using the assay described in Example 1 along with other candidate inhibitors. In a first test, Example 2, the effect of certain carbohydrates on the A. viscosus T14V-S. sanguis 34 coaggregation was determined including glucuronic acid and polygalacturonic acid. The results are summarized in Table 1 below.
As Table 1 shows, lactobionic acid (4-[beta-D-galactosido]-D-gluconic acid) inhibits coaggregation at very low concentrations (3-4 mM), similar to that observed with lactose, a known plaque inhibitor. It was also noted that lactobionic acid also promotes a rebound effect as its concentration is increased up to 100 mM, resulting in 10% inhibition at the higher concentration. A similar rebounding effect was also observed with glucuronic acid which showed significant coaggregation inhibition (15 mM). Polygalacturonic acid (molecular weight estimated at between 4000-6000) effected 50% inhibition at 0.1% (approximately 2 mM).
In a second test, Example 3, a number of water-soluble gums and polysaccharides were examined by the assay of Example 1 for their ability to inhibit coaggregation of A. viscosus T14V-S. sanguis 34 including xanthan gum, guar gum, gum tragacantb, pectin, gum karaya, chondroitin sulphate and certain carrageenans. Gum tragacanth contains mostly galacturonic acid. The results are summarized in Table 2 below.
As Table 2 shows, xanthan and guar gums, and gum tragacanth were the most effective of the tested wherein concentrations of 0.05%, 0.15%, and 0.35% respectively effected 50% inhibition of coaggregation. Pectin and chondroitin sulphate effected almost 50% inhibition at 0.8% and 4%, respectively. Agar and agarose did not demonstrate inhibition. The inhibition by sodium alginate was substantial. Soluble starch and iota carrageenans demonstrated poor inhibition. The lambda carrageenans did not exhibit inhibition but the kappa/lambda carrageenans demonstrated significant inhibition.
Amicon, Vortex, IEC, Sigma and FMC are registred trademarks.

Claims

1. The use of a polysaccharide selected from xanthan gum, gum tragacanth, pectin guar gum, gum karaya, chondroitin sulphate, polygalacturonic acid, sodium alginate and carrageenans of kappa or lambda configuration as an agent for inhibiting plaque.

2. The use of a polysaccharide selected from xanthan gum, gum tragacanth, pectin guar gum, gum karaya, chondroitin sulphate, polygalacturonic acid, sodium alginate and carrageenans of the kappa or lambda configuration in the manufacture of a plaque inhibiting composition, in which the polysaccharide is the sole anti-plaque agent.

3. The use of a polysaccharide according to claim 1 or 2 in the form of a mouthwash, spray or rinse, or a toothpaste, dental cream or tooth powder.

4. The use of a polysaccharide according to any one of claims 1 to 3, in a composition comprising an aqueous medium in which the polysaccharide is present in an amount from 0.0025% to 4.000% by weight of the total weight of the composition.

5. The use of polysaccharide according to claim 4, wherein the aqueous medium is an alcohol/water mixture.

6. The use of a polysaccharide according to claim 5, wherein the ratio of water to alcohol is from 1: 1 to 20: 1.

7. The use of a polysaccharide according to any one of claims 1 to 6, in a composition which further comprises a fluorine-providing compound.

8. The use of a polysaccharide according to any one of claims 1 to 7, is a composition which further comprises a flavourant.

9. The use of a polysaccharide according to any one of claims 1 to 8, in a composition which further comprises a colourant.

10. The use of a polysaccharide according to any one of claims 1 to 9, which further comprises a natural or artificial sweetener.

11. A method for inhibiting the formation of plaque comprising contacting dentin with an oral composition containing an effective amount of a sole anti-plaque agent, which agent is a polysaccharide selected from xanthan gum, pectin gum tragacanth, guar gum, gum karaya, chondroitin sulphate, polygalacturonic acid, sodium alginate and carrageenans of kappa or lambda configuration.

12. A process for the preparation of an oral composition for inhibiting plaque which comprises incorporating into a suitable pharmaceutically acceptable carrier as the plaque-inhibiting agent an effective plaque-inhibiting amount of a polysaccharide selected from xanthan gum, gum tragacanth, pectin, guar gum, gum karaya, chondroitin sulphate, polygalacturonic acid, sodium alginate, and carrageenans of kappa or lambda configuration.

13. A process according to claim 12, wherein the composition is in the form of a mouthwash, spray or rinse, or a toothpaste, dental cream or tooth powder.

14. A process according to claim 12 or 13, wherein the composition comprises an aqueous medium and the polysaccharide is present in an amount from 0.0025% to 4.000% by weight of the total weight of the composition.

15. A process according to claim 14, wherein the aqueous medium is an alcohol/water mixture.

16. A process according to claim 15, wherein the ratio of water to alcohol is from 1: 1 to 20: 1.

17. A process according to any one of claims 12 to 16, wherein the composition further comprises a fluorine-providing compound.

18. A process according to any one of claims 12 to 17, wherein the composition further comprises a flavourant.

19. A process according to any one of claims 12 to 18, wherein the composition further comprises a colourant.

20. A process according to any one of claims 12 to 19, wherein the composition further comprises a natural or artificial sweetener.